Follow the path from the layby and turn right at the junction (all the other bouldering is along the leftwards path). Go up to towards Houndkirk Tor proper but break off left before the main rocky bit as it's impossible to see it from above.
You must have done. If I remember correctly it's just down and right of a green slab - probably the biggest part of the outcrop. But you can't really see it until you're right next to it! Took me a while to find too